Methods and Devices For Usage of Sunscreen Lotions

ABSTRACT

A method for calculating a rate of UV radiation absorbed by a user&#39;s skin including: capturing image data of an area of the user&#39;s skin; determining a skin tone of the user&#39;s skin based on the captured image data; calculating a rate of UV radiation absorption for the determined skin tone; measuring an amount of UV radiation exposed to the user&#39;s skin; and calculating a rate of UV radiation that would be absorbed by the user&#39;s skin based on the user&#39;s skin tone and the amount of UV radiation exposed to the user&#39;s skin. The method can further comprise calculating an amount of time that the user can be exposed to the amount of UV radiation exposed to the user&#39;s skin based on predetermined criteria. The predetermined criteria can at least include an SPF level of sunscreen applied to the user&#39;s skin.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods and devices for the userspecific usage of sunscreen lotions and in particular, methods anddevices for alerting a user with a given skin tone of the generally safelength of time to stay in the sun given the amount of ultraviolet (“UV”)radiation present and the SPF value of the sunscreen lotion or for a SPFvalue of the sunscreen being used how long it is safe to stay under thesun with a given UV radiation level for the user skin tone.

SPF stands for “Sun Protection Factor” and refers to the theoreticalamount of time you can stay in the sun without getting sunburned. Forexample, an SPF of 15 would allow you to stay in the sun 15 times longerthan you could without protection.

Furthermore, “sunscreen” for purposes of this disclosure, means anylotion disposed on the skin and used in the sun to reduce the amount ofUV radiation reaching the treated surface that would otherwise reachwithout such lotion.

Still further, although the description is written in terms of the sunbeing the source of UV radiation, other sources are possible, such assun lamps.

2. Prior Art

In just the last generation, people have become more aware of thedangers of the sun, including aging of the skin, unsightly blemishes,wrinkling, and of course, cancers. All of these dangers have in commonthe exposure of too much UV radiation from the sun, usually resulting ina sunburn. A sunburn is reddening (and possibly inflammation) of theskin that occurs after you are exposed to the sun or other UV light. Asunburn can range in severity from a first degree burn where the skin ispink to bright red and painful, to a second degree burn where the skinis blistered, to a third degree burn where deep cell damage occurs tothe skin and nerve endings can be destroyed. Over exposure to UVradiation from the sun can also result in heat stroke and sun-poisoning.

However, people are still constantly burned by the UV rays of the sun,even those wearing sun-screen lotions. Sunscreen lotions have beendeveloped with varying levels of protection from UV radiation. Asdiscussed above, these lotions are given an SPF level, which is thetheoretical amount of time you can stay in the sun without gettingsunburned. The problem of burning, for those without a sunscreen isobvious, over exposure to harmful UV radiation of the sun (or even a sunlamp). However, even those that use a sunscreen can also be burnedbecause they are not using the proper SPF. These people use the same SPFregardless of factors that affect the amount of exposure they receive onany given day/time, such as their skin tone and the strength of the UVrays that they are being exposed to.

SUMMARY OF THE INVENTION

Accordingly, a method for calculating a rate of UV radiation absorbed bya user's skin is provided. The method comprising: capturing image dataof an area of the user's skin; determining a skin tone of the user'sskin based on the captured image data; calculating a rate of UVradiation absorption for the determined skin tone; measuring an amountof UV radiation exposed to the user's skin; and calculating a rate of UVradiation that would be absorbed by the user's skin based on the user'sskin tone and the amount of UV radiation exposed to the user's skin.

The method can further comprise calculating an amount of time that theuser can be exposed to the amount of UV radiation exposed to the user'sskin based on predetermined criteria. The predetermined criteria can atleast include an SPF level of sunscreen applied to the user's skin. Themeasuring can comprise measuring the amount of UV radiation exposed tothe user's skin as reduced by the SPF level of sunscreen.

The method can further comprise calculating a required sunscreen SPFlevel for a predetermined exposure time.

Also provided is a method for calculating a SPF level of sunscreenlotion. The method comprising: (a) measuring an amount of UV radiationfrom a radiation source using image data of the UV radiation source witha non-UV spectrum filter disposed between an image sensor for capturingthe image data and the non-UV spectrum filter; (b) covering a testfilter with the sunscreen lotion and repeating step (a) with the testfilter in place of the non-UV spectrum filter; and (c) calculating theSPF of the sunscreen lotion based on the results of steps (a) and (b).

The calculating can be a ratio of the results from steps (a) and (b).

Still further provided is a container comprising: a body forming anenclosure, the body having an open end in fluid communication with theenclosure; a cap for releasably covering the opening; sunscreen lotionhaving an SPF factor disposed in the enclosure; and a filter releasablyconnected to the body, the filter having optical propertiescharacteristic of the sunscreen in the enclosure.

The container can further comprise a label adhered to an outer surfaceof the body, wherein the filter is at least a portion of the label. Thelabel can comprise perforations separating the filter from otherportions of the label. The label can further comprise a tab forfacilitating removal of the filter form the label along theperforations.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the apparatus ofthe present invention will become better understood with regard to thefollowing description, appended claims, and accompanying drawings where:

FIG. 1A illustrates a flow chart of an embodiment of a method for usageof sunscreen.

FIG. 1B illustrates a flow chart of an alternative embodiment of themethod for usage of sunscreen of FIG. 1A.

FIG. 2 illustrates a flow chart for another embodiment of a method forusage of sunscreen.

FIG. 3 illustrates a flow chart for a method of checking an SPF level ofa sunscreen, possibly for use in the methods of FIGS. 1 and/or 2.

FIG. 4A illustrates a device for use in the methods of FIGS. 1, 2 and/or3.

FIG. 4B illustrates a schematic representation of the device of FIG. 4A.

FIG. 5 illustrates a bottle of sunscreen having a removable filter foruse in the methods of FIGS. 1 and/or 3.

FIG. 6 illustrates a plurality of filters for use in the method of FIG.1.

FIG. 7 illustrates a test filter for use in the methods of FIGS. 1and/or 3.

FIG. 8 illustrates a flow chart of an alternative embodiment of a methodfor usage of sunscreen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1A, there is illustrated a flow chart of amethod for calculating an average amount of time that a user can beexposed to a UV radiation level. The method includes a step s100 oftaking digital image data of areas of the skin. The areas of the skincan be representative of areas of exposed skin, such as the cheeks,shoulders, back, thighs, stomach, etc. These areas are representative ofthe user's current skin tone levels, which may include previous sunexposure, i.e., tanning However, the user may also use unexposed skinareas, such as those typically covered by clothing, which are morerepresentative of the user's natural skin tone. The natural skin tonesmay vary the result of the method of FIG. 1A such that less exposuretime is recommended.

Referring briefly to FIGS. 4, there is illustrated a device 400 suitablefor capturing the digital image data in step s100. Although a digitalcamera may be used for capturing such image data, such image data wouldthen need to be uploaded to a device having a processor 416 (at least aportion of which comprises hardware) for carrying out other step(s) ofthe methods disclosed herein. Therefore, the device 400 can be of a typethat includes both an image sensor (e.g., digital camera) and aprocessor to avoid having to transfer the image data/digital images froma first device capturing the image data and a second device processingsuch data. In FIG. 4, such device is represented as a smart phone,having an image sensor/digital camera 402 and an internal processor 416.Other devices having a similar configuration can also be used. Althoughsuch devices do not have to be portable, portability is helpful, such asbeing used at the place of exposure to the UV radiation, such as thebeach, park, playground, outdoor workplace, etc. The smart phone device400 further typically includes a wireless connection to the internet,such as a cellular and/or wireless link; a Bluetooth wireless connectionto other devices (the wireless connection being generally illustrated astransceiver 418), memory 414, a display 404, a speaker 408, anilluminating light, such as an LED 410, a microphone 412 and one or moreinput devices, such as buttons 406 and the display 404 being a touchscreen for controlling the device 400. The device 400 generally includessoftware residing in the memory 414 for running applications, such asthe methods disclosed herein. However, all or some of the software stepscan be carried out by software residing remotely from the device 400,such as a remote server accessed through the wireless connection 418.

Returning now to FIG. 1A, at step s102, the image data captured at steps100 is analyzed and the rate of UV radiation absorption for theparticular skin tone and condition in the image data is calculated. Ifmore than one image is used in the analysis or if the skin tone varieswithin a single image, an average rate of UV radiation for the skin toneis calculated. Step s102 measures the skin type while step s104 measurethe UV irradiance ER (W.m⁻²). The maximum permissible exposure (MPE)expressed J.m⁻² will be a function of the skin type, darker skin levelshaving higher values. The minimal erythema dose (MED) has been found tobe a good predictor of assessing the risk of photo damage and skincancer. These values range from 200 J.m⁻² to 1000 J.m⁻² for white toblack skin tones, respectively.

The Fitzpatric Scale defines seven skin types in terms of their severityto burn in the presence of UV exposure. Type I always burns and nevertans, whereas Type VI, which is deeply pigmented dark brown to black,never burns but tans easily. The Fitzpatrick scale is a numericalclassification scheme for determining the skin color based on aquestionnaire related to an individual's genetic constitution, reactionto sun exposure, and tanning habits. For example, Type I has a numericalscore in the range 0 to 6, whereas score is greater than 35 for skintype VI. The skin type can be determined based on the natural lightphotograph taken with the device 400, such as the smart phone camera402. Image sensors, typically, use a 24 bit word, 8 bits per color torepresent the RGB value of each pixel. For example, black is (0,0,0)corresponding to a numerical value of 0, and white is (255,255,255)giving a numerical value of 16581375. A look-up table of the 7 shades ofskin color from white to black can be defined by a RGB vector (R,G,B).For example, dark brown skin (Type IV) is (51,25,0) while light brown(Type III) is (102,51,0).

At step s104, a UV transmitting spectrum filter is used to cover theimage sensor/camera 402 of the device 400. The filter can be a low-passfilter with a cut-off wavelength of 400 nm. The sensor/camera is thendirected towards the sun and an image is captured. The internalprocessor 416 of the device 400 is then used to calculate the sun UVradiation level for the time of the day, weather conditions, etc. Ingeneral, the sensor/camera 402 needs to be calibrated for the UVradiation level measurement, particularly when a camera is used insteadof a calibrated UV radiation level sensor for such measurements sincemost camera image sensors are coated with filters to filter a portion ofthe UV radiation.

Then, as indicated in the flow chart of FIG. 1A, at the step s106, usingthe estimated rate of UV radiation absorption for the user skin tone andcondition (step s102) and the measured UV radiation level at the userlocation (step s104), the processor 416 of the device 400 calculates theaverage rate of UV radiation that would be absorbed by the user's skin.The processor 416 of the device 400 then calculates the average amountof time that the user can be safely exposed to the radiation level atthat time as a function of the sunscreen lotion SPF level. Theinformation can then be displayed for the user on the display 404,preferably in a user selected format, for example in a table, graph,pictorial, verbally, or the like manner.

According to FDA guidelines (21 CFR 1040.20), developed for sunlampmanufacturers, the maximum recommended exposure time should not exceed avalue which will result in an exposure of four times the minimalerythema dose (MED) for untanned Type II skin (always burns, then tansslightly). This is based on the CDRH Erythema Action Spectrum [proposedaction spectrum of Commission Internationale de L'Eclairage (CIE)modified by CDRH]. The formula for the maximum recommended exposure timeTe is given by

${T_{e}\lbrack{seconds}\rbrack} = \frac{624\left\lbrack {J.m^{- 2}} \right\rbrack}{\sum{V_{i}E_{i}}}$

where Standard MED=156 J.m⁻² at 290 nm, V_(i) is the spectral weightingfactor and E_(i) the irradiance in W.m⁻². Using the direct circumsolarspectrum (ASTM G173-03 reference spectrum), T_(e)=2500 seconds.

The recommended maximum exposure time should not exceed a value whichwill result in an exposure of four times the minimal melanogenic dose(MMD) for untanned Type II skin. This is based on the melanogenic actionspectrum. The formula for determining the recommended exposure timeT_(m) is given by,

${T_{m}\lbrack{seconds}\rbrack} = \frac{1836\left\lbrack {J.m^{- 2}} \right\rbrack}{\sum{J_{i}E_{i}}}$

where the Standard MMD=459 J.m⁻² at 296 nm and J_(i) is spectralweighting factor. Using the direct circumsolar spectrum (ASTM G173-03reference spectrum), T_(m)=7503 seconds.

The exposure times calculated above are for untreated skin, and can bemultiplied by SPF to give the extended exposure time for treated skin.

In the above description of step s108, the estimated amount of time thatthe user may at the time be safely exposed to the existing level of UVradiation is calculated as a function of the sunscreen lotion SPF leveland the information transmitted to the user via one or more of theindicated means. It is, however, appreciated by those skilled in the artthat the estimated exposure time period information may be calculatedand transmitted based on different user input information. For example,the user may already have a sunscreen with a known SPF level. The usercan then enter the information into the device 400 at the time of useand at step s108, the user will be provided with the estimated amount oftime that the user may be safely exposed to the existing level of UVradiation. The time period and possibly the time period for differentsunscreen lotion SPF levels may then be transmitted using one of theaforementioned means as preferably selected by the user. The softwareprovided to the device 400 and either residing in the memory 414 or in aremote server and accessed wirelessly can contain a default mode forpresenting the estimated safe exposure time period.

One method of transmitting the information about the estimated amount oftime that the user may be safely exposed to the existing level of UVradiation is by indicating the estimated numbers of hours and minutes onthe display 404 of the device 400, and possibly with a countdown tozero. Alternatively, the time of the day at which the safe exposureperiod will expire may be displaced and/or set into the device 400 alarmclock. Alternatively one or more of the above methods alone or incombination with other displaced images and/or audio sounds orinstructions or the like may be used. The user would have the option ofselecting the desired method or utilize the default option, which can bethe displayed time of the day at which the exposure is suggested to endas well as the alarm signal being sounded. The processor can alsoinitiate a timer based on the result and display the same on the display404 of the device 400 and further indicate one or more warnings on thespeaker 408 for when the time expires or warnings, which can be set bythe user, for when a predetermined amount of time remains before thetime expires.

Referring to FIG. 2, there is illustrated a flow chart of another methodfor calculating an average amount of time that a user can be exposed toa UV radiation level. In this method, following the steps s100, s102 ands104 described previously, at the step s200, based on the calculatedaverage rate of UV radiation absorption for the user skin tone andcondition (step s102) and the measured level of the UV radiation fromthe sun at the time of the day, and based on the amount of exposure timeindicated by the user (as entered by the user into the device 400, FIG.4), the processor 416 of the device 400 can calculate the requiredminimum sunscreen SPF level that should be used for protection from UVradiation (step s200 in FIG. 2).

In an alternative embodiment, the filter used at the step s104, FIG. 1A,is representative of the sunscreen lotion SPF level. The flow chart ofthis alternative method for calculating an average amount of time that auser can be exposed to a UV radiation level is illustrated in FIG. 1B.In the method of FIG. 1B, after the step s102, in step s109 (replacingstep s104 of FIG. 1A), the sensor/camera 402 of the device 400, FIG. 4,is covered with a spectrum filter corresponding to the SPF of thesunscreen to be used and the sensor/camera 402 is directed towards thesun and an image is captured. The internal processor 416 of the device400 is then used to calculate the level of UV radiation that theselected sunscreen SPF would allow to be absorbed by the user skin atthat time of the day, weather conditions, etc. In general, thesensor/camera 402 needs to be calibrated for the UV radiation levelmeasurement, particularly when a camera is used instead of a calibratedUV radiation level sensor for such measurements since most camera imagesensors are coated with filters to filter a portion of the UV radiation.

Then, as was described for step s106 of the flow chart of FIG. 1A, atstep s110 and using the estimated rate of UV radiation absorption forthe user skin tone and condition (step s102) and the measured UVradiation level reaching the user skin covered with the selectedsunscreen lotion with the SPF level (step s109), the processor 416 ofthe device 400, FIG. 4, calculates the average rate of UV radiation thatwould be absorbed by the user skin. Then at step sill, the processor 416of the device 400 will calculate the average amount of time that theuser can be safely exposed to the radiation level at that time with theselected sunscreen lotion SPF level. The information can then bedisplayed for the user on the display 404, preferably in the userselected format, for example in a table, graph, pictorial, verbally, orthe like manner.

The user can use such time to determine how long he/she will remainexposed to the UV radiation or repeat steps s109-s111 for another SPFlevel. The processor can also initiate a timer based on the result anddisplay the same on the display 404 of the device 400 and furtherindicate one or more warnings on the speaker 408 for when the timeexpires or warnings, which can be set by the user, for when apredetermined amount of time remains before the time expires or employany other aforementioned methods and means of providing the said safeexposure timing information to the user.

Referring to FIG. 5, there is illustrated a bottle of sunscreen lotion500 having a cap 502 for containing the lotion in an interior of thebottle 500. The bottle may also have a label 504 in which a portion 506is a filter representative of the SPF level of the lotion contained inthe bottle 500. The filter 506 can be separated from the label 504 byperforations 508 and a tab 510 that can be grasped by the user tofacilitate removing the filter 506 from the label 504 by tearing theperforations 508. Alternatively, the filter 506 can be attached to thebottle by hanging it around the bottle neck 502 a or merely releasablyadhering the filter to the bottle 500.

Referring now to FIGS. 6 and 7, alternatively, one or more of aplurality of filters 600 or a test filter 700 can also be used in Steps104. With regard to FIG. 6, if the sunscreen lotion manufacturer doesnot provide a filter, a filter can be selected from a plurality offilters 600 corresponding to the SPF of the sunscreen to be used. Suchplurality can include filters corresponding to an SPF 5 (filter 602),SPF 8 (filter 604), SPF 15 (filter 606), SPF 30 (filter 608), SPF 45(filter 610) and SPF 60 (filter 612). Such filters 602-612 are by way ofexample only, more or less can be provided and in the same of differentSPF levels. Also, such plurality of filters 600 can be provided on a keyring (not shown), rivet, etc., such as by passing a portion thereof intoa hole 600 a on each filter so that they are compact and each one can beindividually accessible for use with the image sensor/camera 402. If theuser intends to use an SPF 15 lotion, he/she would select a filter 606corresponding to SPF 15 at step s104. Alternatively, the user can selecta filter corresponding to a random SPF, obtain the results and determineif the results are acceptable. If not, the user can select anotherfilter from the plurality of filters 600 and repeat the method until theresults are acceptable.

Referring now to FIG. 7, the body 702 of the filter 700 can be opticallytransparent and not include any filtering of UV radiation. However, afilm of sunscreen can be applied thereto and the method conducted atstep s104 with such filter. In this case, the actual SPF value of thesunscreen will be used in the method instead of a representative filter.

When the user is not sure about the SPF indicated on a sunscreen lotionbottle, then the user may choose to measure the SPF of the sunscreenlotion. To this end, the user can follow the steps provided in the flowchart of FIG. 3. The user will first smear a small amount of sunscreenlotion on a blank “filter” 700 (step s302) and check the amount of UVradiation with (step s304) and without (step s300) the test filter tosee how much is blocked by the filter to arrive at an SPF of thesunscreen lotion (step s306). It is appreciated by those skilled in theart that the surface of the blank test filter can be relativelyabsorbent of the sunscreen lotion to the level of average human skin innormal conditions. The SPF factor X can be calculated by taking a ratioof the measured irradiance with and without the sun screen applied,provided the two measurements are done with the same camera settings, orwith knowledge of the camera settings, which should be accessiblethrough the raw image (or DNG file format).

It is appreciated by those skilled in the art that since the level of UVradiation received from the sun at a given location is dependent on thetime of the day, weather conditions and the time of the year, when auser intends to expose certain region(s) of his/her skin to the sun UVradiation for a relatively long period of time, then for any one of theaforementioned embodiments, the processor 416 of the device 400 mayaccount for such variation of the UV radiation for the said time period.This can be done by using a stored table in the memory 414 indicatingsuch data, and/or by acquiring such data from a provided server viainternet or other wireless connection, or by using a stored table andthe current weather conditions acquired through the internet or the useror other available sources. Alternatively, the program (application)provided either in the memory 414 on the device 400 or acquiredwirelessly may periodically alert the user to make UV level measurement,i.e., repeat the step s104 of FIGS. 1A and 3 or s109 of FIG. 1B, andupdate to safe time duration for exposure accordingly based on totalaccumulated level of UV radiation exposure. Accumulated effects of UVexposure on any part of the exposed skin are assessed by comparing thearchived images captured in step s100. Typically, the images will besegmented into small areas for comparison. Appearance of localized spotswill be early indicators for increased risk to skin melanoma.

It is also appreciated by those skilled in the art that the program(application) provided on the device 400 may be used to alert the userperiodically to apply another coat of sunscreen lotion depending on theweather condition and/or the time elapsed from the last sunscreen lotionapplication and/or depending on various activities such as swimmingprovided by the user and other similar events and conditions such asplaying in sand, sweating, and the like.

Another embodiment, illustrated in FIG. 8, shows a flow chart of amethod for calculating an average amount of time that a user can beexposed to a UV radiation level. The method includes a step h100 ofplacing a UV reflective patch on the surface of the skin area intendedto be exposed to UV radiation (of the sun or other UV radiation source).The areas of the skin can be representative of areas of exposed skin,such as the cheeks, shoulders, back, thighs, stomach, etc. These areasare representative of the user's current skin tone levels, which mayinclude previous sun exposure, i.e., tanning However, the user may alsouse unexposed skin areas, such as those typically covered by clothing,which are more representative of the user's natural skin tone. An imageof the UV patch and surrounding area is captured at step h100. The UVreflective patch can be nearly centered in the captured image. Step h102computes the average UV irradiance at the skin surface from the measuredaverage reflectance signal from the UV patch, and a priori knowledge ofa reflection coefficient of the UV patch in the UV spectrum of solarradiation. Further, the reflectance signal from the skin region isnormalized using the UV patch signal. This normalized value isrepresentative of the skin tone. For example, a value close to zeroindicates white skin tone whereas a value close to unity indicates adark skin tone, reflecting most of the incident UV illumination.

Using the UV irradiance computed in step h102, the recommended exposuretime T_(m) for the unprotected skin can be calculated using abovereferenced equations. The next step h103 applies the sun screen to skinareas surrounding the UV patch. Step h104 calls for capturing the imageof the treated skin and UV patch through the same UV low pass filterdescribed in step h100. Step h104 also repeats the normalizationsequence outlined in step h102, giving a normalized reflectance valuefor treated skin. In step h105, the ratio of the normalized reflectancevalues for treated and untreated skin is calculated giving the timeextending factor X of the screen protection cream (SPF X). The modifiedsafe exposure time with the treated skin is X times the exposure time instep h102.

Another further feature of the method of FIG. 8 is the capability toarchive the image captured from unexposed areas of the skin to use as abaseline measurement for assessing the accumulated effects of theexposed areas over the person's life time. This data would be valuablein providing information on the early stages of skin melanoma.

While there has been shown and described what is considered to bepreferred embodiments of the invention, it will, of course, beunderstood that various modifications and changes in form or detailcould readily be made without departing from the spirit of theinvention. It is therefore intended that the invention be not limited tothe exact forms described and illustrated, but should be constructed tocover all modifications that may fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for calculating a rate of UV radiationabsorbed by a user's skin, the method comprising: capturing image dataof an area of the user's skin; determining a skin tone of the user'sskin based on the captured image data; calculating a rate of UVradiation absorption for the determined skin tone; measuring an amountof UV radiation exposed to the user's skin; and calculating a rate of UVradiation that would be absorbed by the user's skin based on the user'sskin tone and the amount of UV radiation exposed to the user's skin. 2.The method of claim 1, further comprising calculating an amount of timethat the user can be exposed to the amount of UV radiation exposed tothe user's skin based on predetermined criteria.
 3. The method of claim2, wherein the predetermined criteria at least includes an SPF level ofsunscreen applied to the user's skin.
 4. The method of claim 2, whereinthe measuring comprises measuring the amount of UV radiation exposed tothe user's skin as reduced by the SPF level of sunscreen.
 5. The methodof claim 1, further comprising calculating a required sunscreen SPFlevel for a predetermined exposure time.
 6. A method for calculating aSPF level of sunscreen lotion, the method comprising: (a) measuring anamount of UV radiation from a radiation source using image data of theUV radiation source with a non-UV spectrum filter disposed between animage sensor for capturing the image data and the non-UV spectrumfilter; (b) covering a test filter with the sunscreen lotion andrepeating step (a) with the test filter in place of the non-UV spectrumfilter; and (c) calculating the SPF of the sunscreen lotion based on theresults of steps (a) and (b).
 7. The method of claim 6, wherein thecalculating is a ratio of the results from steps (a) and (b).
 8. Acontainer comprising: a body forming an enclosure, the body having anopen end in fluid communication with the enclosure; a cap for releasablycovering the opening; sunscreen lotion having an SPF factor disposed inthe enclosure; and a filter releasably connected to the body, the filterhaving optical properties characteristic of the sunscreen in theenclosure.
 9. The container of claim 8, further comprising a labeladhered to an outer surface of the body, wherein the filter is at leasta portion of the label.
 10. The container of claim 9, wherein the labelcomprises perforations separating the filter from other portions of thelabel.
 11. The container of claim 10, wherein the label furthercomprises a tab for facilitating removal of the filter form the labelalong the perforations.